If you're using a broadband router, no doubt it contains a hardware-based firewall that's going to be far more secure than any software-based firewall. The snag is that your firewall has to cover every computer connected to your network. Yes, you can set up individual rules for each machine, but some people find it all too difficult to configure their router. Often it's easier to leave the hardware firewall and configure each computer on an individual basis. What is appropriate for you is less appropriate for your young kids. If they connect to your network, you might not want them to leave their computer online, unattended.
PC Tools Firewall Plus 3 has recently been upgraded and this is a superb free personal firewall you can install on each home computer connected to your network. It has a number of features, including a stealth mode so you can stop other computers on the same network from connecting to your machine.
Some parts of Atacama have not received rainfall for 500 years - but a sudden deluge of water upset the Desert's delicate biological balance
Spitzer Space Telescope could not spot Oumuamua, suggesting that it is actually pretty small
Greenland crater one of the 25 largest impact craters on Earth
This long-sought progenitor star was identified in an image captured by Hubble in 2007